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Number Play – Class 6 Mathematics notes, important questions and MCQs

NCERT Class 6 Mathematics, chapter 3. Notes, key terms, important questions with answers and MCQs.

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Chapter overview

Numbers hide many surprises. Playing with digits, sums and patterns builds number sense and quick mental skills.

Number games

  • Numbers can be arranged by size on a number line.
  • Palindromes read the same both ways (121, 4554).
  • Kaprekar's routine with 4-digit numbers always reaches 6174.

Estimation and mental maths

  • Round numbers to estimate sums and products quickly.
  • Supercells: a number larger than its neighbours in a grid.
  • Check answers by estimating first.

Key terms

Palindrome
a number that reads the same forwards and backwards
Estimation
finding an approximate answer
Supercell
a number in a grid that is greater than all its neighbours

Formulas

  • Kaprekar constant = 6174

Important questions with answers

Write the largest and smallest 5-digit palindromes.2 marks

Largest: 99999. Smallest: 10001.

Estimate 4,876 + 3,129 by rounding to the nearest hundred, and compare with the actual sum.3 marks

Rounded: 4,900 + 3,100 = 8,000. Actual sum = 8,005. The estimate is very close.

Apply the Kaprekar routine to 2,915: arrange the digits in descending and ascending order and subtract; repeat. What number do you reach?5 marks

9521 − 1259 = 8262; 8622 − 2268 = 6354; 6543 − 3456 = 3087; 8730 − 0378 = 8352; 8532 − 2358 = 6174; 7641 − 1467 = 6174. We reach 6174 (Kaprekar's constant), which repeats itself.

Quick revision

  • Palindromes read the same both ways.
  • Estimate before calculating.
  • 6174 is Kaprekar's number.

Exam tips

  • Round to the nearest 10 or 100 to estimate.
  • Use digit sums to check additions quickly.

Practice MCQs

  1. Which is a palindrome?

    1. 123
    2. 343
    3. 345
    4. 120
    Show answer

    Answer: (b) 343. Reads the same both ways.

  2. 48 rounded to the nearest 10 is

    1. 40
    2. 50
    3. 45
    4. 48
    Show answer

    Answer: (b) 50. 8 rounds up.

  3. Estimated value of 398 + 203 (nearest hundred) is

    1. 500
    2. 650
    3. 700
    4. 600
    Show answer

    Answer: (d) 600. 400 + 200.

  4. The largest 3-digit palindrome is

    1. 989
    2. 899
    3. 909
    4. 999
    Show answer

    Answer: (d) 999. 999.

  5. Which number is a palindrome

    1. 12312
    2. 12321
    3. 12231
    4. 13221
    Show answer

    Answer: (b) 12321. Reads the same both ways.

  6. Kaprekar's routine on 4-digit numbers ends at

    1. 1000
    2. 4321
    3. 9999
    4. 6174
    Show answer

    Answer: (d) 6174. Kaprekar constant.

  7. How many 2-digit palindromes are there?

    1. 9
    2. 10
    3. 90
    4. 11
    Show answer

    Answer: (a) 9. 11, 22, …, 99.

  8. Using digits 3, 0, 8, 5 once each, the smallest 4-digit number is

    1. 0358
    2. 3058
    3. 3085
    4. 5038
    Show answer

    Answer: (b) 3058. 0 cannot be first.

All chapters of Class 6 Mathematics

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.